Have you traveled abroad lately? International usage charges generally do not appear on your current bill. It can take several bill cycles before you see the charge due to the timing of the usage being reported to CREDO.
Why are there international call charges on my bill when I didn't travel during that time? While your usual monthly mobile plan charges are billed in advance, any other charges are charged to your next bill.
For example, if you used international service during September 21 – October 20 bill period, that charge appears on your November bill which isn't due until December. That means you could have been traveling in September but will not pay the international charges you incurred until December.